System Provides Centralized Control of Cleveland Office-Tower Complex

Consisting of one 18-story building and two five-story buildings connected by a glass atrium, North Point Towers in Cleveland is home to insurance companies, health-care providers, government agencies, and one of the world's largest law firms. Tenant amenities include fitness facilities, a cafeteria, and underground parking.

By 2005, much of the complex's HVAC equipment had been installed for more than 20 years and was operating inefficiently and unreliably. When the facilities manager tried to service or replace the equipment, he was told the parts were obsolete or discontinued and that he would have to purchase an entirely new HVAC system.

CHALLENGES

The facilities manager's biggest challenge was making a decision on a final design. He had three options:

Replace the 22 air-conditioning units, which varied in size from 10,000 to 20,000 cfm, according to the system's original design.

Provide a central-plant chilled-water system using the original condenser-water piping with matched VAV AHUs and variable-speed pumping.

One mechanical room was located on each floor of the West Tower, and two mechanical rooms were located on each floor of the North Tower. Each mechanical room essentially acted as a stand-alone air-conditioning plant. The new system needed to centralize all of the cooling functions in those two buildings.

With installation required to occur without any interruption of day-to-day operations, equipment taken offline for replacement had to be in place, tested, and running when the next business day started.

SOLUTION

North Point Towers opted to create a central-plant chilled-water system controlled by a Trend IQ3 solution. Trend's 963 Supervisor software would serve as the front end, while IQ3xcite controllers would monitor centrifugal chillers, chilled-water coils and spot coolers, chiller evaporator pumps, and condenser pumps.

North Point Towers employed a condenser-water loop with self-contained, water-cooled AHUs and cooling towers with piping to cool the mechanical rooms. The mechanical HVAC contractor, Akron, Ohio-based The K Company Inc., installed a 1,050-ton centrifugal chilled-water plant in the basement of the North Tower. All of the mechanical-room compressors were eliminated. Then, technicians replaced all of the old AHUs with new 16,000- to 20,000-cfm models featuring chilled-water coils.

With this new design, North Point Towers is able to use water-side-economizer free cooling to pump water directly to the coils. Pumped water that previously cooled the compressors now is used as chilled water for cooling. This leaves a single point in each mechanical room that the facilities manager can use to send water into the heat exchanger. During winter, he can use outside temperatures to create chilled water and cool the buildings for free.

The K Co. installed variable-frequency drives (VFDs) on the existing building and tower pumps, as well as on the new AHUs. That allows the Trend controllers to speed up or slow down the VFD motors when needed to maintain a set point, further minimizing the system's energy use.

To ensure that none of the offices' high-end furnishings was damaged, The K Co. created a sterile hallway between service elevators and the mechanical rooms. Temporary flooring was installed and areas were taped off to avoid interaction with the large pieces of equipment technicians needed to move through the corridors. At the end of each work session, the areas were cleaned to ensure tenants experienced no inconvenience or discomfort the next work day.

The K Co. coordinated with the North Point Towers facilities staff to conduct the work during evenings and on weekends. Crews would enter after business hours on Fridays and clear out the mechanical rooms, removing old equipment through service elevators. The new AHUs were taken upstairs in sections and reassembled in the mechanical rooms. Technicians connected and tested the AHUs throughout the night and ensured they were up and running by Saturday morning. The K Co. held weekly meetings with the owner and tenants to ensure schedules and expectations were on track.

RESULT

The Trend system inside of North Point Towers offers centralized control of the entire facility. Most importantly, it provides an economic and scalable solution for the future. There are plans to bring the 18-story East Tower under the Trend system, adding another 600,000 sq ft of office space to be controlled.

Although creating a centralized plant was the most expensive option, it also was the most efficient. The new design enabled the North Point Towers facilities manager to configure the existing cooling tower and heat exchanger to provide free cooling during winter, which drastically reduces the buildings' energy costs. An analysis of the overall kilowatts per ton inside of the central plant showed a significant reduction in energy use over a packaged equipment system.

The new system also has reduced ambient noise inside of the towers considerably, increasing tenant comfort and providing an even more professional environment.

Information and the photograph on this page courtesy of Trend Control Systems.

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